Magnetic resonance tomography is a widespread method for obtaining images of the interior of a body. In this method, the body to be examined is exposed to a relatively strong base magnetic field, for example, with a strength of several tesla. A radiofrequency excitation signal (the so-called B1 field) is emitted using a suitable antenna system, the effect of which is to tilt the nuclear spins of particular atoms resonantly excited by this radiofrequency field through a particular flip angle relative to the magnetic field lines of the base magnetic field. The radiofrequency signal radiated during the relaxation of the nuclear spins, the so-called magnetic resonance signal, is picked up in suitable antenna systems, which may also be the same as the transmission antenna system. The raw data acquired in this way are used in order to reconstruct the desired image data. For position encoding, defined magnetic field gradients are respectively superimposed on the base magnetic field by gradient coils during the transmission and readout, or reception, of the radiofrequency signals. The rapidly switched fields and currents resulting, or used, in this case lead to an interaction with the base magnetic field and/or metallic components of the MR system, so that perturbing vibrations that are detrimental to the imaging may occur in the MR system.
Different types of antenna systems may be used for the transmission and readout, respectively. For example, it is possible to use so-called local coils that may be placed on the patient. It is also conceivable for the local coils to be connected by a suspension system to parts of the magnetic resonance imaging system, for example, the patient table, and for the local coils to be arranged at a maximum distance of a few centimeters from the patient.
Magnetic resonance imaging systems furthermore may have antenna systems that are located at a somewhat larger distance from the patient, for example, a few tens of centimeters. These antenna systems may, in particular, be so-called body coils. The antenna elements of the body coil may be constructed on a support tube that cylindrically encloses a measurement space of the magnetic resonance imaging system (the so-called patient tunnel).
If the antenna systems are mechanically coupled to parts of the magnetic resonance imaging system, the antenna systems will be excited in oscillations during operation of the magnetic resonance imaging system by the vibrations that occur during operation. These oscillations are perceptible in various ways. On the one hand, this may entail influences on the quality of the imaging, or the patient's specific absorption rate (SAR), and on the other hand the antenna systems set in oscillation themselves also emit sound that may possibly be perceived as unpleasant by a patient.